System and apparatus with a memory controller configured to control access to randomly accessible non-volatile memory

ABSTRACT

An apparatus includes a printed circuit board with a plurality of printed circuit board traces, a memory controller mounted on the printed circuit board coupled to one or more of the plurality of printed circuit board traces, a plurality of non-volatile type of memory integrated circuits coupled to the printed circuit board, and a plurality of support integrated circuits coupled between the memory controller and the plurality of non-volatile type of memory integrated circuits.

CROSS REFERENCE TO RELATED APPLICATIONS

This non-provisional United States (U.S.) patent application is adivisional application and claims the benefit of U.S. patent applicationSer. No. 11/847,986 entitled MAIN MEMORY IN A SYSTEM WITH A MEMORYCONTROLLER CONFIGURED TO CONTROL ACCESS TO NON-VOLATILE MEMORY, ANDRELATED TECHNOLOGIES filed on Aug. 30, 2007 by inventors VijayKaramcheti et al., to issue as U.S. Pat. No. 7,761,623. U.S. patentapplication Ser. No. 11/847,986 claims the benefit of U.S. ProvisionalPatent Application No. 60/827,421 entitled SUBSTITUTION OF A PROCESSORWITH A BUILT IN DRAM MEMORY CONTROLLER BY A NON-DRAM MEMORY CONTROLLERTO CONTROL ACCESS TO NON-DRAM TYPE MEMORY MODULES filed on Sep. 28, 2006by inventors Kumar Ganapathy et al, and further claims the benefit ofU.S. Provisional Patent Application No. 60/862,597 entitled EXPANSION OFMAIN MEMORY IN A MULTPROCESSOR SYSTEM WITH A NON-DRAM MEMORY CONTROLLERTO CONTROL ACCESS TO NON-DRAM TYPE MEMORY filed on Oct. 23, 2006 byinventors Kumar Ganapathy et al.

FIELD

This document generally relates to memory controllers and memorymodules.

BACKGROUND

A computing system may include dynamic random access memory (DRAM)integrated circuits (ICs) as part of its main memory. DRAM ICs retaindata information by storing a certain amount of charge on a capacitor ineach memory cell to store a logical one or alternatively, a logicalzero. Over time, and because of read operations, the stored charge onthe capacitor dissipates, in a process often referred to as leaking off.To preserve the stored charge on a DRAM capacitor, and thus maintain theability of the DRAM to maintain its memory contents, the stored chargein the memory cell may be increased through refresh cycles, whichsometimes are performed periodically.

BRIEF DESCRIPTIONS OF THE DRAWINGS

FIG. 1 is a functional block diagram of a computer system with only DRAMDIMMS wherein the memory controllers are physically separate from theprocessors.

FIG. 1A is a functional block diagram of an alternate configuration of amemory controller through the use of subsidiary memory controller chips.

FIG. 2A is a functional block diagram of a computer system withintegrated memory controllers collocated within the processors.

FIG. 2B is a functional block diagram of another computer system withintegrated memory controllers collocated within the processors.

FIG. 3A is a functional block diagram of a card with a memory controllerto control non-DRAM type of memory DIMMS capable of plugging into anexpansion slot.

FIG. 3B is a functional block diagram of a card with a memory controllerand non-DRAM type of memory mounted thereto.

FIG. 4 is a functional block diagram of a non-DRAM type of memorymodule.

FIG. 5 is a functional block diagram of an internet server coupled tothe internet.

FIGS. 6A-6B are functional block diagrams of a support integratedcircuit.

FIG. 7A illustrates a flow chart of a method for upgrading a computingsystem.

FIG. 7B illustrates a flow chart of a method for assembling a printedcircuit board assembly with a memory controller and non-DRAM type ofmemory integrated circuits mounted thereto.

DETAILED DESCRIPTION

In the following detailed description, numerous examples of specificimplementations are set forth. However, implementations may includeconfigurations that include less than all of or alternatives for thedetailed features and combinations set forth in these examples.

For similar memory capacity, dynamic random access memory (DRAM)integrated circuits (ICs) typically consume more power than non-volatilememory integrated circuits, particularly when data is read. Non-volatilememory integrated circuits typically do not require refresh cycles andthus conserve power. To reduce power consumption in system applicationswith a main memory, a non-volatile memory integrated circuit may be usedin place of or as a supplement to a DRAM integrated circuit.

Typically, a write access to non-volatile memory integrated circuitstakes more time than a write access to DRAM integrated circuits. Sometypes of non-volatile memory integrated circuits, such as NOR FLASHEEPROM integrated circuits, may be configured with improved read accesstimes (e.g., twice that of DRAM integrated circuits). In order toaddress differences between read and write performance, a datacommunication protocol may be used that accesses the non-volatile memorymodules in a different manner than DRAM memory modules.

In one configuration, a non-DRAM memory controller and non-volatilememory modules may be introduced into a computer system. Thetechnologies used by non-volatile memory integrated circuits differ fromdynamic random access memory (DRAM) integrated circuits (ICs) in thestructure of their memory cell and in how they store information withinthe cell. These differences may help the resultant computer systemachieve relatively low power consumption characteristics. For example,non-volatile memory integrated circuits typically do not require refreshcycles and thus conserve power. Alternately or in addition, they mayhelp expand the capacity of main memory in the system.

Referring now to FIG. 1, a functional block diagram of a computer systemis illustrated with dual in-line memory modules (DIMMS). The computersystem includes a multiprocessor mother-board 100A. Mounted to themother-board 100A is a plurality of processor sockets 101A-101N.Processors 122A-122N may be inserted into these processor sockets101A-101N. The processor sockets are connected to the interconnectfabric 103 via traces 102A-102N. The interconnect fabric 103 may consistof printed circuit board traces alone or it may include other integratedcircuits. The interconnect fabric 103 may be configured to connect thevarious processors, memory, and I/O together within the mother-board.Portions of the interconnect fabric logic may be embedded within theprocessors and memory controllers.

Additionally mounted to the mother-board 100A are one or more memorycontrollers 107A-107N, 117 connected to the interconnect fabric 103 viatraces 106A-106N. The memory controllers 107A-107N, 117 respectivelycontrol each of the memory channels 123A-123N, 133A-133N. Additionalprinted circuit board traces 110A-110N in each of the memory channels123A-123N, 133A-133N are coupled between the memory module sockets108A-108N and the memory controllers 107A-107N, 117.

One or more DRAM memory DIMMS 109A-109N may be accommodated by thesockets 108A-108N in the memory channels 123A-123N. One or more non-DRAMDIMMS 119A-119N, such as non-volatile random access memory (NVRAM)DIMMS, may be accommodated by the sockets 108A-108N in the memorychannels 133A-133N.

Additionally mounted to the mother-board 100A are one or more I/Osubsystems 105A-105N that are connected to the interconnect fabric 103via traces 104A-104N.

Additionally mounted to the mother-board 100A may be one or moreexpansion (EXP) connectors 121A-121N that may be connected to theinterconnect fabric by traces 120A-120N. In one configuration, one ormore of the expansion connectors 121A-121N are used to upgrade the mainmemory of the mother-board 100A.

In FIG. 1, the memory controllers 107A-107N, 117 are directly coupled tothe sockets 108A-108N in each respective memory channel 123A-123N,133A-133N using the PCB traces 110A-110N. However, memory controllersmay also indirectly couple to the sockets 108A-108N in each memorychannel through secondary memory controllers.

Referring now to FIG. 1A, an alternate memory controller system is usedinstead of the direct memory control provided by the memory controllers107A-107N, 117. The alternate memory controller system includes one ormore primary memory controllers (PMC) 113A for each of several or allmemory control channels, and one or more secondary memory controllers(SMC) 112A-112N, (SNVMC) 132 for each of the one or more primary memorycontrollers 113A.

The one or more primary memory controllers (PMC) 113A connect to theinterconnect fabric 103 via traces 106A-106N. In this configuration, theone or more primary memory controllers 113A are indirectly coupled tothe memory channels 123A-123N, 133A-133N. Each of the one or moreprimary memory controllers 113A connects to the one or more secondarymemory controllers (SMC) 112A-112N, (SNVMC) 132 via interconnect traces111A-111N.

Each of the one or more secondary memory controllers 112A-112N, 132 arecoupled to the DIMM sockets 108A-108N via the printed circuit boardtraces 110A-110N. The one or more secondary memory controllers 112A-112Nmay couple to one or more of the DRAM DIMMS 109A-109N inserted into theDIMM sockets 108A-108N within the memory channels 123A-123N to controlthe read and write access to DRAM memory modules. One or more secondarynon-DRAM memory controllers (SNVMC) 132, such as a secondarynon-volatile memory controller, may couple to one or more of thenon-DRAM DIMMS 119A-119N (such as non-volatile memory (NVRAM) DIMMS)inserted into the DIMM sockets 108A-108N within the memory channels133A-133N to control the read and write access to non-DRAM memorymodules. In some implementations, the secondary non-DRAM memorycontroller 132 is a secondary non-volatile memory controller to controlread and write access to non-volatile memory modules.

Referring now to FIG. 2A, an alternate multiprocessor system andmother-board 100B is illustrated. In FIG. 2A, the external memorycontrollers 107A-107N, 117 of FIG. 1 are moved into the processorpackages 200A-200N, 200P′ as part of a processor with one or moreintegrated memory controllers.

In the multiprocessor system 100B, processor sockets 204A-204P areconnected to the interconnect fabric 103 via the traces 102A-102N. Theprocessor sockets 204A-204N are also connected to the memory channels123A-123N, 133A-133N via traces 110A-110N. In this construction, theprocessor package 200A-200N,200P′ includes both one or more processorelements (MP) 201A-201P and an integrated memory controller (IMC)202A-202N, (INVMC) 212.

The integrated memory controllers (IMC) 202A-202N control read and writeaccesses to DRAM memory modules 109A-109N plugged into the DIMM sockets108A-108N within the memory channels 123A-123N. The integrated memorycontroller (INVMC) 212 controls read and write accesses to non-DRAMmemory modules 119A-119N (such as non-volatile memory modules) pluggedinto the DIMM sockets 108A-108N within the memory channels 133A-133N.

There may be one or more memory controllers within a processor package.

Referring now to FIG. 2B, another alternate multiprocessor system andmother-board 100B′ is illustrated. The multiprocessor system andmother-board 100B′ is similar to the multiprocessor system andmother-board 100B. However in FIG. 2B, the processor package 200P″includes one or more processor elements (MP) 201P with two integratedmemory controllers 202P and 212.

The integrated memory controller (IMC) 202P controls read and writeaccesses to DRAM memory modules 109A-109N plugged into the DIMM sockets108A-108N within the memory channels 123N coupled to the processor200P″. The integrated memory controller (INVMC) 212 controls read andwrite accesses to non-DRAM memory modules 119A-119N (such asnon-volatile memory modules) plugged into the DIMM sockets 108A-108Nwithin the memory channels 133N coupled to the processor 200P″.

As previously discussed, constructions of the multiprocessor systems100A, 100B, and 100B′ may have one or more expansion connectors121A-121N. These connectors may be used to improve system performance byincreasing memory capacity with a daughter card. In some cases, they mayhelp reduce the power consumption of the main memory of the computersystem.

In one configuration, the one or more expansion connectors 121A-121N maybe used to upgrade and expand the main memory of the mother-boards 100A,100B, 100B′.

Referring now to FIG. 3A, a daughter card 300 is illustrated to upgradethe main memory in the computer systems having the mother-boards 100A,100B, 100B′. The daughter card 300 includes a memory controller 302 tocontrol non-DRAM type of memory DIMMS. The daughter card 300 may also bereferred to herein as an expansion board.

One or more expansion boards 300 are respectively connected to the oneor more expansion mother-board connectors 121A-121N in the mother-boards100A, 100B, 100B′ via the edge connector 301. The non-DRAM memorycontroller 302 is coupled to the edge connector 301 via traces 306A-306Non the printed circuit board 300A. The non-DRAM memory controller 302 isconnected to each of the non-DRAM memory channels 307A-307N via traces303A-303N, which, in turn, connect to sockets 304A-304N. Non-DRAM DIMMS305A-305N are then inserted into the sockets 304A-304N to expand themain memory to include non-DRAM type of memory therein. That is, themain memory in the computer system is expanded to be a heterogeneousmain memory with different types of memory integrated circuits therein.

Referring now to FIG. 4, a diagram of a non-DRAM type of memory module305 is illustrated. The non-DRAM type of memory module 305 may beplugged into the memory module sockets 304A-304N in the one or morenon-DRAM memory channels 307A-307N of the expansion board 300Aillustrated in FIG. 3A.

In one implementation, the non-DRAM type of memory module 305 is anon-volatile type of memory module. In this case, the non-DRAM memorycontroller 302 is a non-volatile memory controller. In particular, thenon-volatile type of memory module may include at least one NOR-gateflash electrically erasable programmable read only memory (EEPROM)integrated circuit in one implementation.

In FIG. 4, the non-DRAM type of memory module 305 includes a printedcircuit board 400 having pads of edge connectors 401 (one on each sidefor a DIMM) formed thereon, a plurality of non-DRAM memory chips402A-402N, and a plurality of support chips 403A-403N. The memory module305 further includes a plurality of printed circuit board traces (e.g.,printed wires) 404A-404N and 406A-406L formed on the PCB 400 couplingbetween the non-DRAM memory chips 402A-402N and the support chips403A-403N and between the support chips 403A-403N and the pads of theedge connectors 401.

In one implementation, the memory module 305 is a dual in-line memorymodule (DIMM) and the printed circuit board (PCB) 400 is a DIMM PCB. Thenon-DRAM memory chips 402A-402N may be NOR FLASH EEPROM integratedcircuit chips or some other kind of non-DRAM type of memory integratedcircuit chips.

The plurality of support chips 403A-403N may be used to bufferaddresses, and/or multiplex and de-multiplex data to and from thenon-DRAM memory chips 402A-403N. The plurality of support chips403A-403N may also be referred to herein as a plurality of bufferintegrated circuits 403.

In an alternate implementation, non-DRAM type of memory integratedcircuits 402A-402N (e.g., NOR Flash EEPROM) and support chips 403A-403Nmay be directly mounted onto the printed circuit board 300A of theexpansion board 300 in each memory channel 307A-307N and coupled to thetraces 303A-303N without the circuit boards 400, edge connectors 401,and sockets 304A-304N.

Referring now to FIG. 3B, instead of non-DRAM type of memory modulesbeing coupled to sockets of a printed circuit board, non-DRAM type ofmemory integrated circuits 312AA-312MN (e.g., NOR Flash EEPROM) andsupport chips 313A-313N are directly mounted onto the printed circuitboard 300B as shown. The non-DRAM memory controller 302 is also mountedon the printed circuit board 300B. The support chips 313A-313N arecoupled between the memory controller 302 and the non-DRAM type ofmemory integrated circuits 312AA-312MN.

In one implementation, the non-DRAM type of memory integrated circuits312AA-312MN are non-volatile memory integrated circuits, such as NORFlash EEPROM integrated circuits. In one configuration, read and writeaccesses to a non-volatile memory integrated circuit is asymmetric. Inthis case, a write access to non-volatile memory integrated circuitstakes more time than a read access to non-volatile memory integratedcircuits. Some types of non-volatile memory integrated circuits, such asNOR FLASH EEPROM integrated circuits, may be configured so that readaccess times may be reduced to levels sufficient for use in main memory.

If the system 300′ is an expansion board, the printed circuit board 300Bincludes an edge connector 301 to plug into an expansion socket on amother-board. In this case, the memory controller 302 may couple to theedge connector 301.

While an expansion board may be used to increase the capacity of mainmemory with non-volatile memory as discussed previously, DRAM memorymodules may be swapped out for non-volatile memory modules and DRAMmemory controllers may be swapped out for non-volatile memorycontrollers.

In accordance with the teachings of U.S. provisional patent application60/827,421 filed on Sep. 28, 2006 by inventors Kumar Ganapathy et al.,the main memory of the mother-board 100A of FIG. 1 may be upgraded toswap out DRAM memory modules with non-volatile memory modules in one ormore memory channels. In doing so, relatively low power consumptioncharacteristics may be attained by the resultant computer system. Inthis case (see FIG. 1), non-volatile memory modules 119A-119N areplugged into sockets 108A-108N of the respective memory channel133A-133N.

In one implementation (see FIG. 1), one or more of the respective memorycontrollers of the memory channel with the non-volatile memory modules119A-119N is a non-volatile memory controller 117 to control read andwrite access to the non-volatile memory modules 119A-119N. In anotherimplementation (see FIG. 1A), one or more secondary memory controllersof the memory channel may be a non-volatile memory controller 132 tocontrol read and write access to the non-volatile memory modules119A-119N in the respective memory channel 133A-133N. In yet anotherimplementation (see FIGS. 2A-2B), one or more processors in themultiprocessor system may be replaced with processor packages200P′,200P″ having one or more integrated memory controllers 212, 212and 202P, one or more of which may be a non-volatile memory controller212 to control read and write access to the non-volatile memory modules119A-119N in a respective memory channel 133A-133N.

Referring now to FIG. 6A in accordance with one implementation, asupport integrated circuit chip 313 is illustrated as an instance ofeach of the support chips 313A-313N illustrated in FIG. 3B or supportchips 403A-403N illustrated in FIG. 4. The support integrated circuitchips support (i.e., facilitate) read and write data accesses by thenon-volatile memory controllers to non-volatile type of memory modulesand to non-volatile memory integrated circuits.

The support chip 313 may include a many-to-one bus multiplexer 602 and aone-to-many bus demultiplexer 604. The many-to-one bus multiplexer 602is used to write data onto a data bus 316 such as data buses 316A-316Nillustrated in FIG. 3B or printed circuit board traces 406A-406Lillustrated in FIG. 4. The one-to-many bus demultiplexer 604 may be usedto read data from the data bus 316, such as data buses 316A-316N or theprinted circuit board traces 406A-406L, onto one of many data buses suchas data buses 314A-314N or printed circuit board traces 404A-404Ncoupled to the memory integrated circuits.

Referring now to FIG. 6B in accordance with another implementation, asupport chip 313′ is illustrated as an instance of each of the supportchips 313A-313N illustrated in FIG. 3B or support chips 403A-403Nillustrated in FIG. 4. The support chip 313′ may instead include across-bar switch 606 coupled between the plurality of data buses314A-314N in FIG. 3B or printed circuit board traces 404A-404N in FIG. 4connected to the memory integrated circuits and the data bus 316 such asdata buses 316A-316N illustrated in FIG. 3B or printed circuit boardtraces 406A-406L illustrated in FIG. 4. The cross bar switch 606 is usedto write data onto the data bus 316 or printed circuit board traces406A-406L from the memory integrated circuits. The cross bar switch 616is used further to read data from the data bus 316 or printed circuitboard traces 406A-406L and couple the data onto one of data buses314A-314N or a plurality of printed circuit board traces 404A-404Nconnected to the memory integrated circuits.

Referring now to FIG. 7A, a flow chart of a method for upgrading acomputing system using an expansion board of the form shown in FIG. 3Aor 3B is illustrated.

At block 702, an expansion board having a memory controller is pluggedinto an expansion socket on a mother-board. The memory controller is anon-DRAM memory controller to control read and write accesses tonon-DRAM type of memory modules. In one implementation, the non-DRAMtype of memory modules are non-volatile type of memory modules, such asNOR flash electrically erasable programmable read only memory (EEPROM)for example.

At block 704, a plurality of non-DRAM type of memory modules are pluggedinto memory sockets of the expansion board. The memory sockets arecoupled to the memory controller by way of printed circuit board traceson the expansion board.

At block 706, to access the non-DRAM type of memory modules in theexpansion board, a data communication protocol is used for the non-DRAMtype of memory modules. The data communication protocol to access thenon-DRAM type of memory modules may differ from the data communicationprotocol to access DRAM type of memory modules. If a non-volatile memorymodule is plugged into a memory module socket a data communicationprotocol for accessing non-volatile memory modules may be used toaddress the asymmetry between read and write performance.

In the data communication protocol for accessing non-volatile memorymodules, a feedback status control signal is communicated from anon-volatile memory module to the memory controller to alleviate thenon-deterministic nature of the erase and write operations in thenon-volatile memory modules. With a feedback status control signal, thememory controller can avoid constantly polling the memory module as towhen an erase or write operation is completed. Each feedback statuscontrol signal indicates whether or not a rank of memory in a memorymodule is busy or ready for another access to alleviate thenon-deterministic nature of erase and write operations to non-volatilememory modules.

Referring now to FIG. 7B, a method of assembling a printed circuit boardassembly is illustrated.

At block 712, non-DRAM type of memory integrated circuits (e.g., NORFlash EEPROM) are mounted to a printed circuit board and coupled to theprinted circuit board traces of the printed circuit board.

At block 714, support chips are also mounted onto the printed circuitboard coupled to printed circuit board traces of the printed circuitboard.

At block 716, a non-DRAM memory controller is also mounted on theprinted circuit board and coupled to printed circuit board traces of theprinted circuit board.

The support chips are coupled between the memory controller and thenon-DRAM type of memory integrated circuits. In one implementation, thenon-DRAM type of memory integrated circuits are non-volatile memoryintegrated circuits, such as NOR Flash EEPROM integrated circuits.

If the printed circuit board is manufactured as an expansion board, themethod of assembly of the printed circuit board may further includecoupling or forming an edge connector onto or in the printed circuitboard. In this case, the non-DRAM memory controller may couple to theedge connector.

Referring now to FIG. 5, a block diagram of an internet server 500 and aremote client 501 coupled to the internet 502 is illustrated. Theinternet server 500 includes the mother-board 100A, 100B, 100B′ that hasbeen upgraded by the one or more of the expansion boards 300A or 300Bplugged into the one or more mother-board expansion sockets 121A-121N.Each of the expansion boards 300A include non-volatile memory modules305 plugged into the memory module sockets of one or more added memorychannels to upgrade main memory to include non-volatile memory.

An example of the use of non-volatile memory modules in main memory isnow described. The remote client 501 executes a search query 510 againsta search engine running on the internet server 500 to search for data.In this case, the main memory 512 on the mother-board 100A,100Bassociated with internet server 500 may be more often read than it iswritten. This application behavior permits the use of non-volatilememory modules in lieu of DRAM memory modules. With the mother-board100A, 100B, 100B′ upgraded to include non-volatile memory modules in itsmain memory 512, power is conserved over that of a main memory solelyhaving DRAM memory modules. Additionally, because of the cost advantageof non-volatile memory integrated circuits over DRAM integratedcircuits, the internet server 500 can be configured with the same mainmemory capacity for less money, or alternately, can benefit from highermain memory capacity for the same cost.

While this specification includes many specifics, these should not beconstrued as limitations on the scope of the disclosure or of what maybe claimed, but rather as descriptions of features specific toparticular implementations of the disclosure. Certain features that aredescribed in this specification in the context of separateimplementations also may be implemented in combination in a singleimplementation. Conversely, various features that are described in thecontext of a single implementation also may be implemented in multipleimplementations separately or in sub-combination. Moreover, althoughfeatures may be described above as acting in certain combinations andeven initially claimed as such, one or more features from a claimedcombination may in some cases be excised from the combination, and theclaimed combination may be directed to a sub-combination or variation ofa sub-combination.

A number of implementations have been described. Nevertheless, it willbe understood that various modifications may be made without departingfrom the spirit and scope of the disclosure. Other implementations arewithin the scope of the following claims. For example, the memorymodules and the memory sockets have been described as being dual in-linememory modules (DIMM) and DIMM sockets. However, the memory modules andmemory sockets may have other types of form factors such as singlein-line memory modules (SIMM), for example.

1. A system comprising: a printed circuit board including a first memorychannel having a plurality of DRAM memory modules plugged into a firstplurality of sockets; a first memory controller coupled to the firstplurality of sockets in the first memory channel by a first memorychannel bus with a first plurality of traces, the first memorycontroller to control access to the plurality of DRAM memory modules; asecond memory channel having a first plurality of non-volatile memorymodules plugged into a second plurality of sockets, the first pluralityof non-volatile memory modules to conserve power; and a second memorycontroller coupled to the second plurality of sockets in the secondmemory channel by a second memory channel bus with a second plurality oftraces differing from the first plurality of traces, the second memorycontroller to control access to the first plurality of non-volatilememory modules.
 2. The system of claim 1, further comprising: a thirdmemory channel having a second plurality of non-volatile memory modulesplugged into a third plurality of sockets, the second plurality ofnon-volatile memory modules differing from the first plurality ofnon-volatile memory modules, the second plurality of non-volatile memorymodules to conserve power and expand memory capacity of main memory; anda third memory controller coupled to the third plurality of sockets inthe third memory channel by a third memory channel bus with a thirdplurality of traces differing from the first and second pluralities oftraces, the third memory controller to control access to the secondplurality of non-volatile memory modules.
 3. The system of claim 1,further comprising: a processor coupled to the first memory controllerand the second memory controller.
 4. The system of claim 1, wherein thesecond memory controller is a secondary memory controller; and thesystem further includes a third memory controller coupled between theprocessor and the second memory controller.
 5. The system of claim 1,wherein the first memory controller and the second memory controller areintegrated with a processor into a single package coupled to the firstmemory channel and the second memory channel.
 6. The system of claim 1,wherein a first data communication protocol supports a write access tothe plurality of DRAM memory modules in the first memory channeldifferent from a write access supported by a second data communicationprotocol to the first plurality of non-volatile memory modules in thesecond memory channel.
 7. The system of claim 2, wherein a first datacommunication protocol supports a write access to the plurality of DRAMmemory modules in the first memory channel different from a write accesssupported by a second data communication protocol to the first pluralityof non-volatile memory modules in the second memory channel, and a thirddata communication protocol to access the second plurality ofnon-volatile memory modules in the third memory channel differs from thesecond data communication protocol to access the first plurality ofnon-volatile memory modules in the second memory channel.